Apparatus for controlling the slide movement in long-bed hydraulic presses



y 9 4- E. CANNON 2,353,389

APPARATUS FOR CONTROLLING THE SLIDE MOVEMENT IN LONG-BED HYDRAULICPRESSES Filed March 16, 1943 3 Sheets-Sheet 1 lNVENTOR 562?! daw/van BYAT ORNEYS July 11, 1944. E. CANNON APPARATUS FOR CONTROLLING THE SLIDEMOVEMENT IN LONG-BED HYDRAULIC PRESSES Filed March 16, 1943 5Sheets-Sheet 2 1062 108 c s /a63/ INVENTOR 47,9?! Chm MGM BY 2 d, w P

AT ORNEYS Patented July 11, 1944 APPARATUS FOR CONTROLLING THE SLIDEMOVEMENT LONG-BED HYDRAULIC PRESSES Earl Cannon, Rockville Centre, N.Y., assignor to E. W. Bliss Company, Brooklyn, N. Y., a. corporation ofDelaware Application March 16, 1943, Serial No. 479,308

23 Claims.

This invention relates to improvements in apparatus for controlling theslide movement in long-bed hydraulic presses, and more particularlyrelates to improved means for maintaining the slide of such a presssubstantially in parallelism with the press bed during the advance ordownward movement of said slide despite any die or blank irregularitywhich might tend to induce tilting of the slide.

Any reference in the following specification and claims to parallelismor"non-parallelis is intended to relateto the attitude of the slide of apress relatively to the bed of the press. Any reference herein tolong-bed" presses is, intended to refer to any hydraulic press whereinthe present invention may be employed advantageously to-maintain,substantially, the mentioned parallelism of the slide and bed of thepress.

An important object of the present invention is the provision ofimproved means for automatically effecting compensating variations inthe delivery of liquid to plural rams located at various points alongthe slide of a long-bed press whereby to substantially compensate forinitial inequalities in such delivery caused by unequal resistanceoffered to the advance of the press slide at various points thereon, as,for example, unequal resistance which might be offered by a die ofirregular shape. r

A further object of the invention is the provision of improved means forelectrically con.- trolling apparatus adapted to effect compensatingvariations in the delivery of liquid to such plural rams. The inventiondisclosed herein comprises improved means for accomplishing theforegoing and other objects which should be apparent from thisspecification and the accompanying drawings.

The present invention is a further embodiment of certain featuresdisclosed in my copending applications filed September 26, 1942, andOctober 28, 1942, under Serial Nos. 459,854 and 463,604, respectively,and, in certain respects, constitutes improvements thereover. Saidapplication Serial No. 459,854 has been issued as Patent 2,328,258,dated Aug. 31, 1943. The details of various component parts of thestructure described herein are fully set forth in said co-pendingapplications and therefore the description in the present application islimited to such details as are necessary to an understanding of theimprovements illustrated and claimed herein. The means disclosed in saidco-pending Patent 2,328,258, are chiefly mechanical means which areemployed to effect compensatory transfer of liquid from a liquid supplyfor a ram or rams toward one end of the press slide to a liquid supplyfor a ram or rams toward the opposite end of the slide. The improvementsdisclosed in said co-pending application, Serial No. 463,604, resideprincipally in certain electrical or pneumatic apparatus and circuitswhich are employed to derive a response from non-parallelism and tocontrol such a compensatory transfer of liquid.

The improvements of the present invention are directed toward theprovision of improved electrical, pneumatic and mechanical apparatus andcombinations thereof, adapted to function to maintain substantialparallelism. and being of a character which yields a highly sensitivecompensation to non-parallelism and obviates the use of certain slidingelectrical contacts employed in the structure disclosed in saidapplication No. 463,604.

For the purpose of illustrating the present invention and withoutlimiting the invention thereto, a preferred embodiment thereof is shownin the accompanying drawings, in which:

Figure 1 is a perspective View illustrating the application of thepresent invention to a longbed press;

Fig. 2 is a horizontal sectional view taken substantially on the line2-2 of Fig. 1 and on the line 22 of Fig. 3.

Fig. 3 is a vertical sectional view taken substantially on the line 33of Fig. 2;

Fig. 4 is a. flattened semi-circular sectional view taken on the line4-4 of Fig. 3; and

Fig. 5 is a diagram illustrating the various component parts of thepresent embodiment of the invention and the interconnection of saidparts.

Referring first to Fig. 1, the press with which the invention isillustrated may comprise a long-bed ll provided in a base l2 suitablytied at its opposite ends to a crown l3 by tie-rods I 4 extendingthrough slide housings I5 which serve at least partially, to guide averticallyreciprocating slide l6 and to suitably space apart the saidcrown and bed and to maintain the two latter members fixedly in theirproper relationship. Tie-rod nuts ll preferably are provided at theupper and lower ends (the latter are not visible in the drawings) of thesaid tierods.

The slide I6 is reciprocated in a well understood ,manner by rams Illaand l8b, fixed symmetrically upon the slide toward opposite endsthereof. These rams, as best understood from Fig. 5, may be enlarged attheir upper ends to form ram pistons 19a, [9b and may be urgeddownwardly on their advance strokes by liquid introduced into advancechambers 20a, 20b and upwardly on their return strokes by liquidintroduced into return chambers Zia, 2lb. The said chambers of thegeneral character indicated in Fig. may, of course, be suitably formedwithin the crown [3 of the press.

Separate substantially identical pumping systems are provided forhandling the supply of liquid for operating each of the rams I 8a andNb. Describing in detail only the said pumping system which is relatedtoram l8a, it comprises a continuously-acting pump 22a suitably drivenas by an electric motor (not shown). The said pump receives liquid froma supply tank 23 through pipe 24a and pumps said liquid through pipe 25ainto a distributing slide valve 26a, which, depending upon the positionof a piston 21a therewithin, directs the liquid either through a pipe28a to the ram advance chamber 20a to move the ram I811 downwardly orthrough a pipe 29a to the ram return chamber 2la to move the said ramupwardly, or through a pipe 30a back to the tank 23 when it is desiredthat the ram remain substantially at rest. The mentioned liquiddistribution yielding the said ram movements is controlled largely bythe provision on the piston 21a of three enlarged portions or spools31a, 32a. and 33a and intervening neck portions 34a and 35a.

When it is desired to advance the ram l8a (i. e., move it downwardly) toadvance the slide l6 toward the bed I I and a die and blank thereon, thepiston ZIa'is shifted, by any suitable means, to its extreme leftposition as shown in Fig. 5, whereupon liquid entering the valve 26a,through pipe 25a, passes around neck portion 34a, of the said piston,into pipe 28a, and thence to the ram advance chamber 20a, therebyforcing the ram l8a downwardly while liquid is exhausted from the ramreturn chamber Ila through pipe 29a into the valve 26a, wherein theexhaust liquid passes around neck 35a of said piston to pipe 30a whichcarries it to the tank 23. By shifting the piston 21a, to its extremeright position, the flow of liquid is reversed with respect to the saidram chambers thereby causing the ram l8a to pursue its upward or returnmovement.

When it is desired to arrest the movement of the ram la, the piston 21a,may be moved to its mid-position, in which the several mentioned spoolson said piston close off all liquid communication between the pump 22aand the ram chambers 20a and 21a. However, the liquid, continuing to bedischarged by the pump 22a passes from pipe 25a into interior lateralpassage 36a in the spool 32a, thence through longitudinal passage 3lainto lateral passages 38a, 39a, in the spools 3 la and 33a, whence saidliquid passes into pipe 30a which carries it to the tank 23.

In view of the similarity of the pumping systems for actuating the tworams, the foregoing description is intended to suffice for both. Forthis reason, the similar parts of the pumping systems are givenreference characters, in the drawings and hereinafter in thespecification, differing only in their sumxes, the suffix a beingapplied to parts of the pumping system related to ram I81: and the sumxb being applied to parts of the pumping system related to ram l8b. Bothvalves 26a and 261) function alike and may be constrained to function inunison by having their respective pistons tied together by extensionrods 40a and 40b which preferably are adjustably coupled by a turnbuckle4 I. The said plstonsmay be hifted within their respective valves by anysuitable means to control the reciprocation of th press slide. Suchmeans, for example, may be operated manually, electrically, bycompressed air, or by hydraulic pressure.

As illustrated in the accompanying drawings, an electric solenoid 42 maysuitably be connected as by a pin 43 to an end extension 44 of thepiston 21a. The said solenoid is adapted, when energized, to move thepistons 21a and 21b to their left'po'sitions, as shown in the drawings,to cause downward movement of the press slide I6 Another solenoid 45 maybe similarly connected tothe piston 21b for moving both pistons to theirright positions to cause upward movement of the press slide. The twosaid solenoids, of course, are connected in suitable electric circuitsfor controlling the operation of the press.

The pistons 21a, 2117 may be held yieldably in their mid-positions byany suitable means which, for example, may employ springs or air orhydraulic pressure. As illustrated in the accompanying drawings, aspring-centering device is employed comprising a coil-spring 46 which ispositioned about the extension rod 401) and is compressed betweenwashers 41 which, normally, are held against the end of said spring bycollars 48 formed on or fixed on the rod 40b. A cagelike frame 49 isfixed upon some fixed part of the press or other suitable fixed supportin such position, adjacent the rod 40b, that the latter passes throughholes 50 in the ends of said frame, large enough to freely pass the saidcollars 48 but small enough to confine the washers 41 within the saidframe. Thus, when the pistons 21a and 21b are held in their leftpositions, as illustrated in the drawings, by the energized solenoid 42,the spring 46 is exerting compression upon the right washer 4'! and theright collar 48 which, when the said solenoid is de-energized, willcause the said pistons to move to their mid-positions. A similar, butopposite action of the centering device results when the said pistonsare held in their right position by the solenoid 45 and the latter isthen de-energized.

Although the pumping systems for operating the ram [8a ad MD, as thusfar described in detail, may be substantially identical in design, itwill be appreciated that, where resistance to the advance of the slideis not uniformly distributed thereover, the different slippages in thetwo pumps, slight leakages, and possibly other factors, would cause theside or end of the press slide encountering the least resistance toadvance ahead of the other side thereof and this uneven advance orcocking of the slide, in manw instances, would become more pronounced asthe slide progressed toward the end of its advance stroke. This highlyundesirable functioning of the press may be substantially obviated bycompensating means now to be described in detail.

An important feature of this invention is the provision of quick actingautomatic means for substantialy equalizing the supply of liquid to thewhich carries the liquid supply to ram advance chamber 20a and connectedby a pipe 53 to the pipe 28b which carries the liquid supply to ramadvance chamber 201:.

. herein described in detail.

The compensator pump may be a continuously-acting reversible pumpsuitably driven as by an electric motor (not shown) The said compensatorpump further is preferably provided with a pumping mechanism which isadjustable, by movable means which extend to the exterior of the pumpitself, for reversing the flow of liquid through the pump and forcontrolling the volume of such flow. Although various types of pumpshaving. pumping mechanisms conforming to these preferred characteristicsmay be used, a pump of the so-called "Hele-Shaw type such as isillustrated and described in my said co-pending application, Serial No.459,854, is well suited to the purpose of the present invention.

As the particular control mechanism employed in the compensator pump isnot an essential part of the present invention, the said pump is not Itis sufficient to observe for present purposes that the flow of liquidthrough the pump 5i may 'be reversed and the volume thereof controlledby a reciprocating control member 54which extends from the interiormechanism of said pump to the exterior thereof and is operativelyconnected to an extension 56 of a piston 51 of an air motor 58, by alever 55 which is *pivotally supported at a fulcrum point 55a. The saidmotor, as hereinafter explained, is automatically operated in suchmanner as to regulate the direction and volume of flow of liquid throughthe compensator pump 5| in order to derive a transfer of a'suitablevolume of liquid from the liquid supply of one of the mentioned rams tothe liquid supply of the other of said rams whereby to substantiallyrestore and maintain parallelism of the press slide during its advancemovement. a

The supply of air, as a driving medium, to the air motor 58, ispreferably controlled by means of an air distributing valve 59 and anair release valve 60. In carrying out the present invention it ispreferable to provide electrical means for operating the valves 59 and'60, which electrical means may conveniently be arranged to respond tonon-parallelism of the press slide and to control the operation of theair motor 58- so that the latter may operate the control means of thepump 5| to give to the latter its desired compensating effect.

The piston 51 of the air motor 59 has two spools or piston heads 6i! andMr integrally formed therewith or fixedly secured thereupon and isarranged to reciprocate within a bore in an elongated casing 62. Thesaid bore is of different diameters at various points therealong to forma central air chamber 63 and certain oppositelyacting air chamberslocated toward opposite ends of said casing, namely, balancing chambers641 and 641', driving chambers 65!, 65r, and drain chambers 66! and661'. All the mentioned chambers in the air motor 59, as shown in Fig.5, are

provided with suitable ports which. in the case of the drain chambers661, '661 afford communication between said chambers and the freeexterior air, and in the cases of the other mentioned chambers affordmeans of connecting the latter to a compressed air line and to the airvalves 59 and 50.

Similar oppositely-acting centering sleeves -6ll,

611' are accurately fitted to slide upon the piston 51 outwardly of thespools 6| 1, 6H and are accurately fitted to slide within annular webs60!, 681* which separate thesaid balancing and driving chambers atopposite ends of the air motor. The

said centering sleeves have annular flanges 61 at their outer ends forlimiting the sliding movement of said sleeves.

Another pair of similar oppositely-acting sleeves 691, -69r areaccurately fitted to slide upon the piston 5'! at points between thespools 6|! and Mr. These sleeves have similar annular flanges 69! ontheir inner ends, the said flanges being :granged to work within thecentral air chamber The air distributing valve 59 is very similar to thehydraulic distributing valves 26a and 26b. It comprises a piston 10,having three spools H, l2, 13 formed on or fixed thereon, and accuratelyfitted to slide within a bore 14 in a casing I5. The said spools defineneck portions 16 and 11 on said piston. The valve 59, as shown in Fig.5, is provided with suitable ports, which may be covered and uncoveredby the spools ll, 12, 13, when the piston 10 is moved to variouslongitudinal positions, and which afford means for connecting theinterior of the valve 59 with the free air and with various ports of therelief valve 69 and the air motor 58. The valve 59 may be provided witha centering spring 18 which operates to center the piston 10 in the samemanner as the spring 46 functions to center the pistons of the hydraulicvalves 26a and 26b. The piston I0 is connected to oppositely-actingsolenoids I9, 80, which are connected in circuits, hereinafterdescribed.

The air release valve 60 comprises a piston 8| having two spools 82, 83,accuratel fitted to reciprocate within a bore 84 of a casing 85. Thesaid spools define a neck portion 8 la therebetwe'en. The casing 85, asshown in Fig. 5, is provided with several ports affording means forconnecting the interior of the bore 84 to free air and to pipes leadingto the air motor 58 and the valve 59. The piston is normally urgedtoward the right by a compression spring 96 and is movable toward theleft against the compression of said spring by means of a solenoid 81which is suitably connected to said piston. The said solenoid isconnected in electric circuits, hereinafter described.

In order to mechanically detect any non-parallelism of the press slideIS, a pair of verticallydisposed racks 08 (see Fig. 1) are secured attheir lower ends to slide l6 toward opposite ends thereof. The saidracks may be guided within suitable guides 89 fixed upon the crown l3and are the said racks and shafts at opp site ends of the press slide isof similar step-up characteristics so that if the press slide remains inparallelism as it descends, the shafts 901 and 90rrotate to similardegrees; if the slide tilts as itdescends, one of said shafts rotates toa greater degree than the other. The two mentioned shafts are supportedwithin brackets 94 fixed upon the crown l3.

A differential mechanism 95 is employed between the shafts 901 and 901'as may best be understood from Fig. 1. The said mechanism may be of aconventional type, as shown in Fig. 2. It comprises bevel gears 961 and961', keyed respectively upon the inner ends of shafts 901 and 901' andmeshing with bevel. differential gears 91 which are mounted within acage 99 upon studs 99. The cage 99 preferably is freely mounted uponshafts 901 and 90r and is confined between a pair of said brackets 94,the mounting being such that the said cage is capable of rotationrelatively to said shafts.

It should be apparent that if theparallelism.

of thepress slide I6 is maintained as it descends,

the shafts 901 and 901' move in similar degrees but in oppositedirections, so that the rotation passage of light rays from the severalincandescent lamps to the several photoelectric cells.

imparted to the differential gears 91 by the bevel gear 961, tending toturn the cage 99 in one direction, is exactly counteracted by therotation imparted by the bevel gear 991 to said differential gears,tending to turn said cage in its opposite direction. It, hen'ce, resultsthat while the slide I6 moves downwardly in parallelism with the bed II, the cage 99 remains at rest.

0n the other hand, if the slide I9 does not maintain its parallelism asit moves downwardly, one of the shafts 901 or 901' turns to a greaterdegree than the other, thus, through the differential gears 91,imparting a. rotative movement to the cage 98 in a direction and to anextent which depends upon the direction and extent of tilting of thepress slide. The mentioned movement of the differential cage isemployed, in the present invention, to control various electric circuitswhich, on their part, control apparatus adapted to operate theflow-controlling mechanism ofthe compensator pump ii to substantialymaintain parallelism of the press slide. The movement of saiddifferential cage also functions,

in a manner hereinafter explained, to stop the press if tilting of thepress slide should go beyond certain predetermined limits which may beconsidered dangerous or detrimental to the press. The manner in whichthe mentioned differential cage movement controls these functions is nowIt is preferred to provide, within the casing I02, a pair of similaropaque partitions I09 which, as best seen in Figs. 1 and 2, are disposedparallel to and closely adjacent the opposite faces of the disc I00.These partitions preferably are U shaped and extend from the crown l9into intimate engagement with the casing I02, to which they may bewelded, and also extend substantially about the differential cage 99. Asecond pair of U shaped partitions I04 may be welded or otherwise fixedto the inner edges of the partitions I03 and extend outwardly therefrom,normally to the latter, into intimate engagement with covers I05 whichmay be secured, as by bolts I06 to the casing I02 and to the crown I3 ofthe press.

The fixed partitions I03 and the disc I00 are suitably apertured in amanner hereinafter described and function together as a shuttermechanism. On one side of said mechanism, a plurality of light sources,which are disclosed herein as four incandescent lamps I01, I09, I09, H0,

The disposition of the said apertures may best be understood from Figs.3 and 4. Apertures in the form of radial slots I0'I:1:, I08a:, I09a:,H03: are located similarly in the partitions I03 in alignmentrespectively with the lamps and cells I0'|-I0Ic, I09-I080, I09--I09c,and IIO--I0c. The disc I00 is provided with a plurality of radialapertures in the form of slots I0'Iy, I091], I09y, I092, IIOy and H02,which are located on said discsubstantially as shown in full lines inFig. 3, which figure also clearly shows the relationship of saidapertures to the apertures I012, I09zc, I090: and 0.1:, whichare'indicated therein in broken lines.

The location and relationship of the various mentioned apertures is alsomade clear in Fig. 4 which also shows clearlythe relationship of saidslots to the several pairs of incandescent lamps and photoelectriccells. The latter' figure, it should be remembered, is a flattenedsemi-circular sectional view taken on the line 4-4 of Fig. 3, and,hence, counterclockwis movement of the disc I00 as viewed in Fig. 3appears as upward movement thereof in Fig. 4, while the clockwisemovement of said disc appears as downward movement thereof in Fig. 4.

In Fig. 4, the disc I00 is shown in the position in which it is set andremains while the press slide I9 is parallel to the press bed II. If inthe operation of th press the left side of the slide I9, during its downstroke, moves ahead of the right side thereof, the disc I 00 will turnto some extent in a clockwise direction as viewed in Fig. 3. ordownwardly as viewed in Fig. 4.

Even a relatively slight non-parallelism of the particular characterjust mentioned will cause aperture I09y to move at least partially intoalignment with apertures I09:1:, thus permitting light rays from lampI09 to pass to cell I09c and cause the latter to function in an electriccircuit in a manner hereinafter described. If such non-parallelismbecomes more pronounced, aperture I09y will move into at least partialalignment with apertures I09:c, thus permitting light rays from lamp I09to pass to cell I090. If such non-parallelism becomes still morepronounced and is of such magnitude as to be dangerous or otherwiseobjectionable, aperture H011 moves into at least partial alignment withaperture 0.1:, permitting light rays from lamp H0 to pass to cell IIOc.

If, in the downward movement .of the press slide the right side' thereofmoves ahead of the left side thereof, movement of the disc I00 wouldoccur in the opposite direction, i. e., counterclockwise as viewed inFig. 3, and upwardly as viewed in Fig. 4. The latter character ofnonparallelism would result, first in alignment of aperture I0'ly withapertures I0'I:c to permit passage of light rays from lamp I01 to cellIIIlc; then if such non-parallelism were to become more pronounced,aperture I092 would move into alignment with apertures I091: to permitpassage of cell I I00.

The embodiment of the present invention disclosed herein includes otherelectric apparatus and electric and hydraulic circuits which may beunderstood from the following explanation of the operation of theapparatus.

In practice, the 'parts of the described apparatus are so assembledthat, when the slide I6 and the bed I I are perfectly parallel, theapertures in partitions I03 and in the disc I are in the relativepositions shown in Fig. 4 so that no light rays may pass to any of thephotoelectric cells, and the pistons of the air valves 59 and 60 and ofthe air motor 58 are all in the positions indicated in Fig. 5 ofthe'drawings.

If the press is open and it is desired to cause the press slide I6 tomove downwardly to perform a pressing operation, th operator sets switchI I4 to its "down position, as shown in Fig. 5, thereby closing acircuit from main lead H5 (indicated as a negative lead), through switchH4, wire H6, the coil of solenoid 42, wire H1, normally-closedcontactors I42a, of relay I42, and wire H8, to main lead I2I which isindicated as a positive lead. Automatic or semiautomatic means may beand usually are provided for controlling the circuits through solenoids42 and 45, but such means are not described herein as they constitute nopart of the present invention.

Upon the closing of the mentioned circuit through solenoid 42, thelatter is energized and draws the pistons of the hydraulic valves 26a,26b to their left positions as shown in Fig.5, whereupon liquid from thepumps 22a, 22b passes through said valves and through pipe lines 28a,28b to ram advance chambers 20a, 20b, respectively, thus causing ramsI61: and I8b to descend with the slide I6, the liquid from returnchambers 2Ia, 2Ib, meanwhile, being exhausted through pipes 29a, 29b tothe valves 26a, 26b and thence through pipes 30a, 30b to the tank 23.

The closing of switch H4 to its down position also establishes twocircuits through the several incandescent lamps. The first of saidcircuits extends from main lead H5 through switch H4, wires H6, H9, lampH0, and wire I20 to main lead I2); thus lamp H0 is lighted at all timeswhen switch I4 is in down position. The second of said circuits extendsfrom main lead H5 through switch H4, wires H6, H9, I22, normally closedcontactor I42b of relay I42, wire I23, lamps I01, I08, I09, and wire I20to main'lead I2I; thus lamps I01, I08, I09 which are connected inparallel in this circuit, are lighted at all times when switch I I4 isin down" position, except when relay I42 is energized in a mannerhereinafter described. v

For present purposes it may be supposed that the press contains a die ordies of such irregular vertical dimensions. or that the blank is of sucha character, that th slide I6, in its downward movement, meets a greaterresistance to such movement toward its right and thus inducing, in thepump 22b, a greater slippage than is present in the pump 22a, with theresult that the latter pump passes a somewhat greater volume of liquidinto ram advance chamber 20a than is passed into ram advance chamber 20bby the pump 22b with the result that the left side of the slide I6 tendsto move downwardly ahead of the right side thereof, thus giving theslide an objectionable tilting attitude which may impair the precisionof the pressing operation as aifecting the blank and which, in anyevent, introduces very objectional friction and consequent wear in theslide guides of the press.

However, immediately upon the inception of such uneven descent andbefore the tilting of the press slide becomes objectionable in anypractical sense, the shaft 901 rotates somewhat more than the shaft901', thus imparting to the disc I00, of the shutter mechanism, aclockwise motion as viewed in Fig. 3 (downward motion as viewed in Fig.4), causing the aperture I081; to move into alignment with apertures I082:, thus permitting light rays from lamp I08 to pass to cell I080 thusactivating the latter to complete, in a well understood manner, circuitsfrom said cell through wires I24, I25 to a suitable amplifier I26 andfrom the latter, by suitable wiring, through the coil of relay I21.

The mentioned circuit through. the coil of relay I21 energizes the saidcoil and causes the contactor I21a of said relay to move from itsnormally open position to closed position, thus completing a circuitfrom main lead I I5, through wire I28, the coil of solenoid 19, wireI29, contactor H111 and wire I30 to main lead I2I. Upon the closing ofthe said circuit through solenoid 19, the latter is energized and drawsthe piston of air distributing valve 59 toward the left against thetension of spring 18 to a position in which compressed air from air lineI3I may freely enter the valve 59 through pipe I34 and pass along andaround neck portion 11 of the piston 10, whence it may pass out of thevalve 59 through pipe I32 into driving chamber 651' of the air motor 68.

As will be seen from Fig. 5, the balancing chambers 641, Mr are directlyconnected to air line I3I, hence the air pressure in said balancin'gchambers functions normally to maintain the piston 51 of the air motorin its mid position, as shown in the drawings, by air pressure exertedon the outer ends of the sleeves 6", 611', which press at their innerends against the spools 6Il, 6Ir, respectively. However, when thecompressed air at the same pressure is introduced into drivingchamber-651, in the manner just described, the force of said pressureexerted upon the right side of the spool 6I1', is greater than thedifierence between the forces of the pressure on the left and rightsides of the flange 61f of the sleeve 61!, hence the piston 51 is driventoward the left until the spool 6Ir engages the right end of the sleeve691' but proceeds no further inasmuch as the force of the air pressurewithin the central air chamber 63, which is normally connected to airline I3I through pipe I33 and valve 60, exerts a greater force uponsleeve 691' than the difference in the forces applied to the spool 6Irin the chamber 651' and to ,"t'he sleeve 611 in the chamber 641.

The mentioned limited shifting of the piston 51 to the left in themannerjust explained causes the lever 55 to turn about its fulcrum 55a andmove the control member 54 of the reciprocating pump 5| to the right,and the connection of the said control member to the said pump is suchthat the latter pumps liquid through pipes 53 and 52 from the primaryliquid supply of ram 'I8a to the primary liquid supply of ram I8b.

This pumping action of the pump 5|, resulting from the limited shiftingof the piston 51 of the air motor 58 and the consequent limited controlchange in the compensator pump may transfer sumo-lent liquid from oneside of the press to the other to fully compensate for the pre-existinginequalities in the volumes of liquid supplied to the opposite side ofthe press, with the result that the slide I5 of the press is restored toparallelism with the press bed II. While such restoration is takingplace, there occurs a counterclockwise movement of the disc I00, asaresult of which aperture I081 moves out of alignment with aperturesI08r, thus cutting off the light beam to cell I080. This causes thelatter to become deactivated, thus opening the mentioned circuitsthrough the amplifier I26, the coil of relay I21, and the solenoid I9,thereby deenergizing the latter and permitting the piston 10 of the airdistributing valve 50 to be restored to its mid-position shown in Fig. 5by the centering spring I8.

In the said mid-position of the position 10, the spool I2 closes oilpipe I34 while driving chamber 551' of the air motor is connected toexhaust port I35 of the air valve 59 through air pipe I32 and throughthe interior of valve 59 wherein the exhaust air from chamber 551' maypass around neck portion 1'! to said exhaust port I35 and pass throughthe latter to free air. Upon chamber 551' of the air motor beingconnected to free air in the manner just described, the air pressure inthe balancing chamber 54! functions to move sleeve 6" to the right,carrying the piston 51 with it back to the latters mid-position, asshown in the drawings. The said movement of the mentioned piston, ofcourse, restores the control member 54 of the compensator pump 5I to itsnormal position in which the pumping mechanism of said pump, althoughbeing driven by its motor, is nevertheless not passing any liquid.

If, after the discontinuance of the pumping action of the compensatorpump 5|, the irregularity of the die or blank causes the left side ofthe press slide I6 again to move ahead of the right side thereof, thedescribed apparatus again functions in a. similar manner to bring thecompensator pump into play to again restore the parallelism of the pressslide. This compensat- 'ing action may conceivably take place a numberof times during theadvance of the press slide so that, during saidadvance, the press slide pursues an almost imperceptible rocking action.The latter action, of course, is restrained within permissible limits sothat, in so far as any material considerations are concerned, th pressslide is maintained in parallelism with the bed of the press during itsentire advance movement.

If the irregularity of the die or blank is such as to cause the rightside of the press slide Hi to advance slightly ahead of the left sidethereof, the compensator pump and the controls thereof function in amanner similar to that just described but various parts are actuated inopposite directions to achieve the desired opposite compensation. Whennon-parallelism of the latter character occurs the disc I00 turns tosome extent in a counterclockwise direction so that aperture I0Iyregisters with aperture I013: to permit light rays from lamp I01 to passto and activate cell I010. Th latter cell is connected through amplifierI35 and relay I31 to solenoid 80 similarly to the previously recitedconnections of cell I080 to solenoid I9, hence, when cell I0'lc iactivated as a result of the mentioned counterclockwise rotation of discI00, solenoid 00 is energized causing the piston of the air distributingvalve 59 to be moved to the right instead of to the left, so thatcompressed air is introduced into chamber 651 of the air motor 58instead of into chamber 551- thereof, thereby causing the piston of saidair motor to move toward the right. This latter movement causes thereciprocating control member 54 of the compensating pump to move to theleft whereby to cause the pumping mechanism of said pump to transferliquid from the primary liquid supply of ram l8b to the primary liquidsupply of ram I8'a, thus restoring the parallelism of the press slide.

It may occur in practice that die or blank irregularities or otherconditions may be such as to cause a more pronounced or objectionabletilting of the press slide than the permissible tilting which thecompensating means thus far described is adapted to compensate. Suchobjectionable tilting may be of such magnitude that, if we assume theleft side of the press slide to be moving in advance of the right sidethereof, not only would cell I 080 be activated by the clockwiserotation of the disc I00, but such rotation would be suflicient to alsobring aperture I09y into alignment with apertures I09: to permit lightrays from lamp I09 to pass to and activate cell I090 which, as may beseen from Fig. 5, is connected through amplifier I38 and relay I39 withthe coil of solenoid 81. Thus, in the event of such excessive tilting ofthe press slide, the solenoid 81 is energized and moves piston 8| of airrelease valve 60 toward the left against the compression of spring 85,causing spool 83 to close ofl air line I3I from communication with theinterior of said valve and at the same time affording a passagepermitting air from central air chamber 63 of the air motor 58 toexhaust through pipe I33 into release valve 60, whence said exhaust airpasses around and along the neck portion of the piston BI and escapes tofree air through exhaust port I40.

Upon the opening of central air chamber 53 of the air motor 58 toexhaust, the sleeve 59r which theretofore functioned as a stop, limitingthe sliding movement of the piston 51 to the left, becomes free to moveto the left within chamber 53 thus permitting a further movement of thepiston 51 to the left, in addition to the limited sliding movementpreviously pursued by said piston, in response to air introduced intochamber 551'. This further movement of the piston 51 to the left causesa corresponding further movement of the reciprocating control member 54of the compensator pump, toward the right, thus increasing thecompensating flow of liquid through the pump 5| to yield sumcientadditional compensation to overcome the excessive tilting of the pressslide and restore it to parallelism. It will be observed from Figs. 3, 4and 5 that the aperture I081; is of suflicient width that cell I080remains activated to maintain air pressure in chamber 551 of the airmotor 58 while cell I09c is activated in the manner and for the purposesjust described whereby to yield the mentioned additional slidingmovement of the piston 51 when pressure in the chamber 53 is released.Aperture I0'Iy similarly is of sufficient width to yield a likeadditional sliding movement of the piston 51 to the right if thecompensation desired is opposite to that just described.

side thereof, the disc I turns in a counterclockwise direction andbrings aperture I092 instead of aperture I09y into alignment withapertures I09x; thus, regardless of which side of the press slide ismoving ahead when excessive tilting is present, the solenoid 01 isenergized to shift the piston ill of the air release valve 60 toward theleft, in the manner already described, to exhaust the air and relievethe pressure from central air chamber 53 of the air motor 58. Suchrelease of pressure in said chamber permits sleeve 501 to move towardthe right when the piston 51 is being urged toward the right, therebypermitting said piston to move beyond said initial limited movement,causing a corresponding increase in the movement of the reciprocatingcontrol member 54 of the compensator pump to the left so that the flowof liquid through said pump, in the proper direction, is increasedsufficiently to yield the desired increased compensating effect.

Under some conditions it may be feasible to dispense with the airrelease valve 60. If this is done, the apparatus employed would be sodesigned and adjusted that the compensator pump 5|, under anyanticipated operating conditions, would fully yield the compensatingeffect necessary to restore the parallelism of the press slide as theresult of a single shift of the control member 54. However, if thecompensating capacity of the compensator pump 5| is stepped upsufliciently to cause adequate compensation in all instances, inresponse to the activation of only one of the cells I0'Ic or I080,compensation would occur very rapidly and consequently the mentionedrocking of the press slide, under some circumstances, might beobjectionably rapid, and

during a single advance stroke of the slide might occur so frequently asto be objectionable.

The air release valve is advantageous in that, by its use, a completestroke of the piston 51 of the air motor 58 and consequent extremeadjustment of the control member 54 of the compensator pump, isaccomplished in two distinct steps rather than in one step. If excessivetilting of the press slide occurs, the mentioned two step adjustmentsyield the maximum compensating effect necessary to restore the pressslide to para lelism; However, the tilting of the press slide, in manycases, may be effected before becoming excessive, by the efiect of onlyone step of compensator pump adjustment. It follows that when only thelower compensating effect. of a single step of compensator pumpadjustment, is brought into play, the rocking action of the press slideis much slower and not frequent enough to be objectionable.

It may be understood from the foregoing explanation of the effects oftoo rapid compensation that it is important to so correlate the movementof the piston 51 of the air motor 58 to the movement of thereciprocating control element of the compensator pump that only theproper degree of compensation is obtained. In order to readily permitcorrelation of these movements it is preferable to provide a variablefulcrum point for the lever 55. A suitable variable fulcrum arrangementis fully disclosed and described in my mentioned co-pending applicationSerial No. 463,604.

Ordinarily, compensation takes place through the activation of eithercell I0Ic or I08c, and where additional compensation is necessary it isordinarily derived from the activation of cell I090; However, if somepart of the system were to fail, with the consequent failure of thecompensating mechanism, or if for any other reason compensation shouldnot take place and the tilting of the press slide were to progresssufflcientiy IIOz into alignment with apertures IIOrc, thus permittinglight rays from lamp IIO to'pass to cell 00. The light thus activatessaid cell and causes it, through amplifier I ll and relay I42 to movethe contactors I42a and I421) of said relay from their normally closedto open positions.

The opening of contactor I42a breaks the electric circuit throughsolenoid 42, whereupon the pistons of the several hydraulic distributingvalves assume their mid-positions, thus stopping the movement of thepress slide. The opening of cont-actor I42bbreaks the electric circuitthrough the lamps I01, I 08, I09, thus deactivating cells I0jIc, I080and I09c, assuring that the solenoids 00, I9 and B1, controlledrespectively by said cells, permit the pistons of air valves 50 and 60to move to the positions shown in Fig. 5 so that the compensator pumpadjustment is shifted back to neutral or non-pumping position. Thus thecell Ili c fuctions as a safety device to stop the operation of thepress.

It is well known by those familiar with the art relating to hydraulic,pr'esses, that suitable means in the form of drain or bypass ducts orclearances must be provided in certain portions of the various valvesand the air motor to prevent locking thereof. Such means, however,'arenot essential features of the present invention and, therefore, have notbeen fully illustrated in the drawings.

It should be understood. of course, that the invention may be employedin presses using more than two rams and that the use of a compensatorpump or pumps may be avoided in some installations, by adapting theelectric or pneumatic ap paratus, or both, to function directly with thepumps provided for supplying liquid to the several ram chambers, wherebyto effect compensation directly in said pumps. The invention may bepracticed in these and many other ways without, however, departing fromthe substance of the invention as defined in the accompanying claims.

What I claim is: I

1. Apparatus for substantially maintaining parallelism of two relativelymovable pressing members in a press, said apparatus comprising anelectrical system, means controlled by said system for moving saidpressing members into parallelism, photoelectric means associated withsaid e ectrical. system, and an operating member, adapted to moveoperatively in either of opposite directions relatively to paths oflight to said photoelectric means, in response to departure of saidpressing members from parallelism, whereby to oppositely modify theoperation of said-photoelectric means and electrical system. and therebyto move said pressing members into parallelism.

2. Apparatus for maintaining parallelism of a s ide member and a bedmember relatively to each other in a long-bed press during the closingthere of, the said apparatus comprising compensating means coacting withone of said members for varying the attitude thereof relatively to theother of said members, and an electric control system adapted to controlthe operation of said compensating means, thesaid system including photoelectric means and a member, for operatingthe latter means, adapted torespond operatively to non-parallelism in either of opposite directionswhereby to cause said compensating means substantially to remedy suchnon-parallelism.

3. Apparatus for maintaining parallelism of a slide member and a bedmember relatively to each other in a long-bed press during the closingthereof, the said apparatus comprising compensating means coacting withopposite sides of one of said members for varying the attitude thereofrelatively to the other of said members, and an electric control systemadapted to control the operation of said compensating means, the saidsystem including photoelectric means and a member, for operating thelatter means, adapted to respond operatively to non-parallelism ineither of opposite directions whereby to cause said compensating meanssubstantially to remedy such nonparallelism.

4. Apparatus for controlling the slide movement in a long-bed presshaving a plurality of slide-actuating means, the said apparatuscomprising compensating means for efiecting compensating variations inthe operation of said actuating means during the advance movement of thepress slide, and an electric control system adapted to control theoperation of said compensating means, the said system includingphotoelectric means and a member, for operating the latter means,adapted to respond operatively to non-parallelism of the press slide ineither of opposite directions whereby to cause said compensating meansto eifect compensation in the operation of said actuating means,substantially to remedy such non-parallelism,

5. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating rainsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for eii'ecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means and a member, for operating the lattermeans, adapted to respond operatively to non-parallelism of the pressslide in either of opposite directions whereby to cause saidcompensating means to efiect compensation in the volume of liquid pumpedinto said chambers substantially to remedy such non-parallelism.

6. Apparatus according to" claim 5, further characterized in that itincludes a pair of movable members coacting with the press slide atopposite sides thereof and with said operating member to operate saidphotoelectric means whereby to control the operation of said electricsystem and, through the latter, to control said compensating means.

7. Apparatus according to claim 5, further characterized in that thesaid compensating means comprise a movable member adapted to control thesaid compensating variations, and in having driving means coacting withand adapted to actuate said movable member, the said electric controlsystem being adapted to control the said driving means, and, throughcontrol of the latter, to control the said compensating means to remedynon-parallelism of the press slide.

8. Apparatus for controlling the movement of a press slide comprisingactuating means for actuating said slide, an electric circuit adapted tocontrol said actuating means, photoelectric means in said circuit andadapted to control the latter, an operating member, operativelyresponsive tonon-parallelism of said slide in any one of pluraldirections and adapted to operate said photoelectric means and, throughthe latter, to control said actuating means whereby to stop the movementof said slide when non-parallelism of the latter goes beyond apredetermined degree.

9. Apparatus for controlling the attitude of a slide of a pressrelatively to a bed thereof, comprising compensating means coacting withsaid slide for effecting compensating variations in such atttitude, aphotoelectric cell adapted to control said means, and a shutter memberadapted to be moved, operatively, in response to changes in suchattitude in anyone of plural directions whereby to so control thepassage of light to said cell as to cause said compensating meanssubstantially to maintain parallelism of the press slide and bed.

10. Apparatus according to claim 9, further characterized in that saidshutter member has an open space and coacts with the press slide tomove, with the departure of the latter from parallelism, betweenregistering and non-registering positions of said open space withreference to a path of light to said cell.

11. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related'ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for effecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism of Ithe press slide whereby to cause said compensating means to effectcompensation in the volume of liquid pumped into said chamberssubstantially to remedy such non-parallelism, the said apparatus beingfurther characterized in that the said photoelectric means comprise ashutter member coacting with opposite sides of the press slide andadapted to move in response to differences in the movements. of saidopposite sides whereby to so control the passage of light in saidphotoelectricmeans as to cause said electric control system andslide-actuating means to remedy nonparallelism.

12. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for effecting compensating variations,during the advance movement of the press slide, in the volume of liquipumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism ofthe press slide whereby to cause said compensating means to effectcompensation in the volume of liquid pumped into said chamberssubstantially to remedy such non-parallelism, the said apparatus beingfurther characterized in that it includes a pair of rotatable shafts,driving means at each or opposite sides of the press slide controlled bythe movement of the latter and adapted to coact with and separatelyrotate said shafts, during the advance movement of the slide, to degreeswhich correspond r difier in accordance with the parallelism ornon-parallelism of the slide, a movable member operably connected toboth said shafts and adapted to be moved by the latter in either of twodirctions depending upon the differences in degrees of rotation of saidshafts, and in that the said photoelectric means comprise a shuttermember constrained to move with said movable member whereby to controlthe passage of light in said photoelectric means, and, through thelatter, to control the said compensating means; a I

13. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprisingaseparate pumping system for each of'said chambers adapted to pump liq-,uid thereto, compensating means for effecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism ofthe press slide whereby to cause said compensating means to effectcompensation in the volume of liquid pumped into said chamberssubstantially to remedy such nonparallelism, the said apparatus beingfurther characterized in that'it includes a pair of rotatable shaftscoacting with and driven by opposite sides of the press slide, and adifferential mechanism connected operably between said shafts, and inthat the said photoelectric means comprise a shutter member adapted tobe rotated by said diflferential mechanism in a direction and to anextentcorresponding to the differential direction and extent of rotationof said mechanism whereby to control the passage of light in saidphotoelectric means.

14. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pumpliquidthereto, compensating means for'efiecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectirc means adapted to respond to non-parallelism ofthe press slide whereby to cause said compensating means toefiectcompensation in the volume of liquid pumped into said chamberssubstantially to remedy such nonparallelism, the said apparatus beingfurther characterized in that the said compensating means comprise amovable member adapted to control the said compensating variations, andin having a'fiuid-actuated motor coacting with and adapted to actuatesaid" movable member, the said electric control system being'adapted tocontrol the said motor, and, through control of the latter, to controlthe said compensating means to remedy non-parallelism of the pressslide.

15. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for etfecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism ofthe press slide whereby to cause saidcompensating means to effectcompensation in the volume of liquid pumped into said chamberssubstantially, to remedy such non-parallelism, the said apparatus beingfurther characterized in thatthe said coin-, pensating means comprise amovable member adapted to control said compensating variations to adegree corresponding substantially to the degree of movement of saidmovable member, and in having driving means for moving said movablemember, the said driving means having plural, separately controllablestages of operation, and the said photoelectric means including pluralphotoelectric cells, each responsive to different degrees ofnon-parallelism of the press slide and adapted to control the saidseparate stages of operation of said driving means.

16. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for effecting compensating variations,during the advance movement'of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism ofthe press slide whereby to cause said compensating means to efiectcompensation in the volume of liquid pumped into said chamberssubstantially to remedy such non-parallelism, the said apparatus beingfurther characterized in that the said compensating means comprise amovable member adapted to control said compensating variations to adegree corresponding substantially to the degree of movement of saidmovable member, and in'having driving means for-moving said movablemember, the said driving means comprising a fluid-actuated motorincluding a casing, and a piston adapted to reciprocate within saidcasing, the casing having separate chambers for fluid for causing pluralstages of movement of said piston in one direction, and the saidphotoelectric means including plural photoelectric cells, eachresponsive to difierent degrees of nonparallelism of the press slide andadapted to control the supply of fluid to said separate chambers, inaccordance with the degree of nonparallelism of the press slide,

17. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the said apparatus comprising aseparate pumping system for each of said chambers adapted to pump liquidthereto, compensating means for effecting compensating variations,during the advance movement of the press slide, in the volume of liquidpumped into said chambers, and an electric control system adapted tocontrol the operation of said compensating means, the said systemincluding photoelectric means adapted to respond to non-parallelism ofthe press slide whereby to cause said compensating means to'eflectcompensation in the volume oi! liquid pumped into said chamberssubstantially to remedy such non-parallelism, the said ,apparatus .beingfurther characterized in that the said compensating means comprise amovable member adapted to control said compensating variations to adegree corresponding substantially to the degree of move-. ment of saidmovable member, and in having driving means for moving said movablemember, the said drivingmeans comprising a fluid-actuated motorincluding a casing, and a piston adapted to reciprocate within saidcasing, the casing having separate chambers for fluid for causing pluralstages of movement of said piston in each direction, and the saidphotoelectric means including plural-photoelectric cells, eachresponsive to diiierent direction and degrees of non-parallelism or thepress slide and adapted to control the supply of iiuid to said separatechambers in accordance with the direction and degree of non-parallelismof thepress slide.

18. Apparatus for controlling the slide movement in a long-bed hydraulicpress having a plurality of symmetrically-disposed slide-actuating ramsand related ram advance chambers, the

said apparatus comprising a separate pumping system for each.- of saidchambers adapted to pump liquid thereto, compensating means forefiecting compensating variations, during the advance movement of thepress slide, in the volume of liquid pumped into said chambers, and anelectric control system adapted to control the operation of saidcompensating means, the said system including photoelectric meansadapted to respond to non-parallelism of the press slide whereby tocause said compensating means to efiectcompensation in the volume ofliquid pumped into said chambers ubstantially to remedy suchnon-parallelism, the said apparatus being further characterized in thatthe said compensating means comprise a reversible pump connected betweenram advance chambers at of liquid pumped into said chambers, and anelectric control system adapted to control the operation of saidcompensating means, the said system including photoelectric meansadapted to respond to non-parallelism of the press slide whereby tocause said compensating means to effect compensation in the volume ofliquid pumped into said chambers substantially to remedy suchnon-paralelism, the said apparatus being further characterized in thatthe said electric control system includes a compensation-con trolcircuit having a first photoelectric cell therein and being adapted tocontrol said compensating means, and a safety circuit having asecondphotoelectric cell therein and being adapted to control the advancemovement of the press slide, the said first cell being adapted torespond to a to cause said compensating means to eilect compensation,and the said second cell beingadapted to respond to non-parallelismbeyond a predeattitude, a photoelectric cell adapted to control,"

said means, and a shutter member adapted to be moved in response tochanges in such attitude whereby to so control the passage or light tosaid cell as to cause said compensating means substantially to maintainparallelism of the press slide and bed, the said apparatus being furthercharacterized in comprising a plurality of such cells, a first one ofsaid cells being adapted to control a first stage of compens'ationinsuch attitude, and a second one of said cells being adapted 'to controla second stage of such compensation, and characterized further in thatthe said shutter member has at least one open space related to each ofsaid cells and coacts with the press slide, upon its departure fromparallelism, to cause a space in said shutter member, related to saidfirst cell, to move between registering and nonregistering positionswith reference to a path of light to said first cell to cause a firststage of compensation, and coacts with the press slide,

upon a greater departure thereof from parallelism, to cause a space insaid shutter member, related to said second cell, to move betweenregistering and non-registering positions with referenceto a path oi.light to said second cell to cause a second stage of compensation.

21. Apparatus for controlling the attitude of a slide of a pressrelatively to a bed thereof, comprising compensating means coacting withsaid slide for eflecting compensating variations in such attitude, aphotoelectric cell adapted to control said means, and a shutter memberadapted to be moved in response to changes in such attitude whereby toso control the passage of light to said cell as to cause saidcompensating means substantially to maintain parallelism of the pressslide and bed, the said apparatus being further characterized in having,actuating means for actuating said press slide and in having, a secondphotoelectric cell adapted to control said actuating means, and furthercharacterized in that the said shutter member has at least one openspace related to each of said cells and coacts with the press slide,upon its departure from parallelism, to cause a shutter space, relatedto the cell adapted to control the said compensating means, to movebetween registering and non-registering positions with reference toapath of light to the last-mentioned cell to cause compensation of thepress slide, and coacts with the press slide, upon a greater departurethereof from parallelism, to cause a space in said shutter member,related to said second cell, to move between registering andnon-registering positions with reference to a path of light to saidsecond cell to render the slideactuating means inoperative in order tostop the movement of the press slide.

22. Apparatus for controlling the attitude of a slide of a pressrelatively to a bed thereof, coniprising compensating means coactingwith said slide for effecting compensating variations in such attitude,a photoelectric 'cell adapted to conpredetermined degree ofnon-parallelism whereby trol said means, and a shutter member adapted tobe moved in response to changes in such attitude whereby to so controlthe passage of light to said cell as to cause said compensating meanssubstantially to maintain parallelism of the press slide and bed, thesaid apparatus being further characterized in having actuating means foractuating said press slide and in having a first cell for controllingthe compensating means to yield compensation in one direction, a secondcell for controlling the compensating means to yield compensation in theopposite direction, and a third cell for controlling said actuatingmeans, and further characterized in that the said shutter member has atleast one open space related to each of said cells and coacts with thepress slide, upon its departure from parallelism in one direction, tocause a shutter space, related to said first cell, to move betweenregistering and non-registering positions with reference to a path oflight to said first cell to cause compensation tending to restoreparallelism, and coacts with the press slide, upon its departure fromparallelism in the opposite direction, to cause a shutter space, relatedto said second cell, to move between registering and non-registeringpositions with reference to a path of light to said second cell to causecompensation tending'to restore parallelism, and coacts with the pressslide, upon. a greater departure thereof from parallelism in either ofsaid directions, to cause a shutter space, related to said third cell,to move between registering and nonregistering positions with referenceto a path of light to said third cell, to render the slide-actuatingmeans inoperative in order to stop the movement of the press slide.

23. Apparatus for controlling the attitude of a slide of a pressrelatively to a bed thereof, comprising compensating means coacting withsaid slide for eflecting compensating variations in such attitude, aphotoelectric cell adapted to control said means, and a shutter memberadapted to be moved in response to changes in such attitude whereby toso control the passage of light to said cell as to cause saidcompensating means substantially to maintain parallelism of the pressslide and bed, the said apparatus being further characterized in havinga pair of shafts coacting with opposite sides of the press slide toderive rotation in opposite directions, a differential mechanismoperatively connected between and driven by said shafts, a difierentialmember in said mechanism adapted to rotate in accordance with thedifierential of the rotation of said shafts and in that the shuttermember is disc-like and is "constrained to rotate with said differentialmember and has at least one open space adapted to move betweenregistering and non-registering positions with reference to a path oflight to said cell.

EARL CANNON.

. CE'RTIFICATE OF CORRECTION. Patent No. 2,555,589. July 11, 19141;.

EARL CANNON.

It is hereby certified. that error appears in the printed specificationof the above,numbered patent requiring correction as follows: Page 2,sec- 0nd column, line '50, for "ad" read and--; line 59, for ."manw"read -many--; page 5, first column, lines 15 and 114., for "application,Serial No. 159,35lu' read --Patent No.-2,528,258; page 1;, secondcolumn, line 1 for "10" read --ll0c--; page 6, first column, line 22,for "position 70" read piston TO--; and that the said Letters Patentshould be read with this correction therein that the same may conform tothe record of the case in the Patent Office.

si ned and sealed this 29th day of August, A. D. 19%.

Leslie Frazer (Seal) Acting Commissioner of Patents.

